HK1247677B - Virtual machine cloning method and device under kvm virtualization - Google Patents

Description

A method and device for cloning virtual machines under KVM virtualization

Technical Field

The present application relates to the field of cloud computing, and more specifically, to a method and apparatus for cloning virtual machines under KVM virtualization.

Background Art

A virtual machine is an application running on a Windows or Linux computer that "simulates" the environment of a standard x86-based PC. This environment, like a regular computer, includes a chipset, CPU, memory, graphics card, sound card, network card, floppy drive, hard drive, optical drive, serial and parallel ports, USB controllers, and SCSI controllers. The "window" that displays this application is the virtual machine's display. A portion of the hard drive and memory is allocated to create multiple virtual machines within a single computer, each capable of running a separate operating system without interfering with each other. These "new" machines each have their own independent CMOS, hard drive, and operating system. Users can partition, format, install operating systems, and other software on them just like regular machines, and even connect these operating systems to form a network. A virtual system crash can be directly deleted without affecting the local system, and similarly, a local system crash will not affect the virtual system; the previously created virtual system can be reinstalled and added later. It is also the only virtualization software that runs on both Windows and Linux host platforms. Virtual machine software allows you to use multiple operating systems on the same computer without having to reboot, making it both convenient and secure.

In public cloud environments, virtual machines (VMs) sometimes need to be created and deployed quickly, such as for VM-level traffic balancing. These VMs often run identical systems and applications, and a significant portion of their memory is shared between them to conserve memory usage. Rapid VM cloning technology can clone a VM in seconds, and VMs share memory in a Co-Work (COW) fashion. Existing VM cloning technology provided by VMWare only works within VMWare's virtual environments. However, in the KVM (Kernel-based Virtual Machine) virtualization environment, there is no viable fast VM cloning solution. Therefore, a method for fast VM cloning in KVM virtualization is urgently needed.

Summary of the Invention

In view of this, the technical problem to be solved by the present application is to provide a method and device for cloning virtual machines under KVM virtualization.

In order to solve the above technical problems, the present application provides a method for cloning a virtual machine under KVM virtualization, including:

Pausing a first virtual machine and saving data of the first virtual machine in a designated memory; wherein the data in the designated memory is not released;

Obtaining startup parameters of the virtual machine executable program from the designated memory;

The virtual machine executable program is started to clone the second virtual machine.

The step of starting the virtual machine executable program to clone the second virtual machine includes:

Create a child process, which calls the virtual machine executable program;

The virtual machine executable program is started and initialized, and the second virtual machine is obtained after the initialization is completed.

The creating of the child process includes: the parent process corresponding to the first virtual machine inheriting the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

The step of obtaining startup parameters of the virtual machine executable program from the designated memory includes:

The state information of the first virtual machine is obtained from the designated memory, and the state information of the first virtual machine is updated to obtain the startup parameters.

Furthermore, the method further includes: obtaining the address of the designated memory; and passing the address of the designated memory as a new parameter into the startup parameters of the virtual machine executable program.

Furthermore, the method further includes: the child process and a parent process corresponding to the first virtual machine share a page table in a copy-on-write manner.

Furthermore, the method further includes: outputting the unfinished IO when the first virtual machine is suspended to a storage medium.

Furthermore, the method further includes: acquiring data of the first virtual machine from the designated memory, and restoring the first virtual machine.

The present application also discloses a method for cloning a virtual machine under KVM virtualization, comprising:

Pausing a first virtual machine and saving data of the first virtual machine in a designated memory; wherein the data in the designated memory is not released;

Starting a virtual machine executable program to clone the second virtual machine;

The data is restored from the designated memory to the first virtual machine.

The step of starting the virtual machine executable program to clone the second virtual machine includes:

A child process is created, and the child process calls a virtual machine executable program; the virtual machine executable program is started and initialized, and the second virtual machine is obtained after the initialization is completed.

The creating of the child process includes: the parent process corresponding to the first virtual machine inheriting the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

Furthermore, the method further includes: the child process and a parent process corresponding to the first virtual machine share a page table in a copy-on-write manner.

Furthermore, the method further includes: outputting the unfinished IO when the first virtual machine is suspended to a storage medium.

The present application also discloses a device for cloning a virtual machine under KVM virtualization, comprising:

A first pre-processing module is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory;

A first parameter acquisition module, configured to acquire startup parameters of the virtual machine executable program from the designated memory;

The first cloning module is used to start the virtual machine executable program to clone the second virtual machine.

The first cloning module is used to: create a child process, and the child process calls the virtual machine executable program;

The virtual machine executable program is started and initialized, and the second virtual machine is obtained after the initialization is completed.

The first cloning module is used to: the parent process corresponding to the first virtual machine inherits the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

The first parameter acquisition module is configured to acquire the state information of the first virtual machine from the designated memory, and update the state information of the first virtual machine to obtain the startup parameters.

The first parameter acquisition module is further configured to: acquire the address of the designated memory; and pass the address of the designated memory as a new parameter into the startup parameters of the virtual machine executable program.

Furthermore, the device further includes a first sharing module, and the first sharing module is configured to enable the child process and a parent process corresponding to the first virtual machine to share a page table in a copy-on-write manner.

Furthermore, the apparatus further includes a first IO output module, and the first IO output module is configured to output unfinished IO operations when the first virtual machine is suspended to a storage medium.

Furthermore, the device further includes a first data recovery module, and the first data recovery module is used to: obtain the data of the first virtual machine from the designated memory and restore the first virtual machine.

The present application also discloses a device for cloning a virtual machine under KVM virtualization, comprising:

A second pre-processing module is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory;

A second cloning module, configured to start a virtual machine executable program to clone the second virtual machine;

The second data recovery module is configured to recover the data from the designated memory to the first virtual machine.

The second cloning module is used to: create a child process, which calls a virtual machine executable program; start the virtual machine executable program and initialize it, and obtain the second virtual machine after the initialization is completed.

The second cloning module is configured to: cause the parent process corresponding to the first virtual machine to inherit the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

Furthermore, the device further includes a second sharing module, and the second sharing module is used for: the child process and the parent process corresponding to the first virtual machine share the page table in a copy-on-write manner.

Furthermore, the device further includes a second IO output module, which is used to output the unfinished IO when the first virtual machine is suspended to a storage medium. Compared with the prior art, the present application can achieve the following technical effects:

1) Saving the data of the first virtual machine to a designated memory with a mark that is not released, thereby enabling rapid modification and update of startup parameters of the child process virtual machine executable program;

2) The child process corresponding to the second virtual machine and the parent process corresponding to the first virtual machine share a page table in a copy-on-write manner.

3) Rapid cloning of virtual machines is achieved by executing the virtual machine executable program in a child process. It naturally shares memory with the original virtual machine based on COW (Copy on Write). The time for rapid cloning of virtual machines is about 100ms-200ms, making it imperceptible to users.

4) While cloning the second virtual machine, the working capability of the first virtual machine is guaranteed.

Of course, any product implementing this application does not necessarily need to achieve all of the technical effects described above at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

FIG1 is a technical flow chart of Example 1 of the present application;

FIG2 is a schematic diagram of the structure of the device according to the first embodiment of the present application;

FIG3 is a technical flow chart of Example 2 of the present application;

FIG4 is a schematic diagram of the structure of the device according to the second embodiment of the present application;

FIG5 is a technical flow chart of an example application scenario of the present application.

DETAILED DESCRIPTION

The following will describe the implementation methods of the present application in detail with reference to the accompanying drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.

Memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and/or non-volatile memory in the form of read-only memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.

Computer-readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. The information can be computer-readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include non-transitory media such as modulated data signals and carrier waves.

For example, certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different terms to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in their functionality. Throughout the specification and claims, the term "including" is an open-ended term and should be interpreted as meaning "including, but not limited to." "Substantially" means that within an acceptable range of error, a person skilled in the art can solve the technical problem and substantially achieve the technical effect. Furthermore, the term "coupled" encompasses any direct and indirect electrical coupling means. Therefore, if a first device is described as being coupled to a second device, this means that the first device can be directly electrically coupled to the second device or indirectly electrically coupled to the second device via other devices or coupling means. The subsequent description of the specification describes preferred embodiments of the present application. However, this description is intended to illustrate the general principles of the present application and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the appended claims.

It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or system. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or system comprising the element.

KVM, short for Kernel-based Virtual Machine, is a virtualization infrastructure used within the Linux kernel. KVM's main functions include CPU virtualization, memory virtualization, and interrupt virtualization. After loading the KVM module in Linux, users cannot directly control the kernel module's operations and must use other tools to create virtual machines.

QEMU, or Quick Emulator, is a widely used open-source computer emulator and virtual machine. When used as a virtual machine, QEMU can directly utilize the system resources of a real machine, enabling the virtual system to achieve performance close to that of a physical machine. However, QEMU's performance is poor when running standalone. By leveraging KVM through interfaces provided by hardware virtualization features, high performance can be achieved.

In KVM virtualization, QEMU is a process running on the host (Linux host) and serves as a container for the virtual machine. The virtual machine runs within the QEMU process, and each virtual CPU (VCPU) of the virtual machine corresponds to a thread of the QEMU process. The memory used by the virtual machine is allocated by the QEMU process on the host. In addition, the QEMU process is responsible for simulating virtual machine devices (such as the network card, keyboard, and mouse). The following section will describe the preferred embodiments of this application in detail with reference to the accompanying drawings.

FIG1 is a technical flow chart of the first embodiment of the present application. In conjunction with FIG1 , the present application provides a method for cloning a virtual machine under KVM virtualization, which can be implemented by the following steps:

Step S110: Pause the first virtual machine and save the data of the first virtual machine to a designated memory; wherein the data in the designated memory is not released

Step S120: obtaining startup parameters of the virtual machine executable program from the designated memory;

Step S130: starting the virtual machine executable program to clone the second virtual machine.

Specifically, in step S110, the Linux kernel is pre-modified to perform some pre-processing before the virtual machine is cloned so that when the virtual machine clone calls the exec function, the pre-specified memory is not released. The specified memory is requested by QEMU on the host machine and has a special mark to serve as an identification mark that it will not be released when the exec call is executed.

When the host machine allocates the specified memory, an identification flag is added to the specified non-released memory. At the same time, by modifying the settings of QEMU, the DONTFORK flag is not specified so that the child process generated by fork() and the parent process corresponding to the first virtual machine share the page table in a copy-on-write manner. The DONTFORK flag is automatically added by default in QEMU. If this flag is added to the memory, the memory will not be inherited to the child process when the child process is created. In this application, the memory of the parent process needs to be inherited to the child process, so that the newly cloned second virtual machine and the original first virtual machine can share memory by adopting this method.

The first virtual machine, i.e., the cloned virtual machine, is paused. After the pause, the data of the first virtual machine at the time of the pause is retained in advance. The data is retained for one purpose to obtain the state information of the first virtual machine from the data, thereby quickly updating the state information to obtain the startup parameters required by the virtual machine executable program when cloning the second virtual machine; the second purpose is to retain the data of the first virtual machine to avoid losing this data when the exec system call is subsequently executed. At the same time, after the first virtual machine resumes operation, it can also be restored to the state at the time of suspension based on the retained data, ensuring that the first virtual machine can operate normally while successfully cloning the second virtual machine. The current data includes the virtual machine state information of the first virtual machine, as well as the memory addresses and video memory addresses used by the first virtual machine. The virtual machine state is the current state information of all devices that the first virtual machine needs to save the state, such as the virtual machine name, universal unique identifier, MAC address, CPU operating status, mouse and keyboard device status, etc. Specifically, in step S120, the startup parameters of the virtual machine executable program are obtained from the designated memory. The virtual machine executable program in the embodiment of the present application can be a QEMU executable program.

The QEMU executable program needs to be configured with some startup parameters before starting, such as VNC (Virtual Network Computer) address, virtual machine name, UUID (Universally Unique Identifier), etc.

In the embodiment of the present application, the startup parameters of the QEMU executable program are modified and updated based on the state information of the first virtual machine. In other words, the state information of the cloned second virtual machine is similar to that of the first virtual machine, and the state information of the second virtual machine can be quickly obtained by simply modifying the state of the first virtual machine.

For example, the MAC address of the network card of the first virtual machine is:

mac＝52:54:00:ce:67:a9, the MAC address of the network card of the second virtual machine can be changed to mac＝52:54:00:ce:67:aa, which can avoid MAC conflicts.

It should be noted that, in the embodiment of the present application, the address of the specified memory with the non-release mark when executing exec needs to be passed as a new parameter into the startup parameters of the QEMU executable program. The purpose is that when the child process executes the QEMU executable program, the memory address and video memory address of the first virtual machine are directly obtained from the specified memory address according to the new parameters in the QEMU executable program for sharing by the second virtual machine.

Specifically, in step S130, a child process representing the new virtual machine, ie, the second virtual machine, is created through fork().

A process consists of code, data, and allocated resources. The fork() function creates a process that is nearly identical to the original process through a system call. This means the two processes can do exactly the same thing, but they can also do different things if the initial parameters or variables passed in are different. When a process calls fork(), the system first allocates resources to the new process, such as space for storing data and code. It then copies all values from the original process to the new process, with only a few values differing from those in the original process.

A single call to the fork function returns two values. It returns once in the calling process (called the parent process), with the process ID of the newly forked process (called the child process); and again in the child process, with a return value of 0. Therefore, the return value itself tells you whether the current process is the child or the parent. The reason fork returns 0 in the child process, rather than the parent's process ID, is that any child process has only one parent, and the child process can always obtain the parent's process ID using getppid. In contrast, a parent process can have many children and cannot obtain the process ID of each child. If the parent process wants to keep track of the process IDs of all its child processes, it must record the return value of each fork call.

It should be noted that the child process created by the fork() function can share memory with the parent process and naturally has the COW (copy on write) feature. At the same time, the flag that the memory is not released when the exec system call is executed in the parent process is also inherited by the child process.

In this step, the child process starts the virtual machine executable program by calling the exec() function. The exec family of functions is used to find an executable file according to a specified file name. The exec system call is often used in conjunction with fork(). First, fork is used to create a child process, and then exec is used in the child process. In this way, the parent process runs a different child process from it, and the parent process will not be overwritten. To execute the exec system call, generally, a new process is first created using the fork() function, and then the newly created process is allowed to execute the exec call. After fork() creates a new process, the parent process and the child process share the code segment, but the data space is separate. However, the parent process will copy the contents of its own data space to the child process, and the context will also be copied to the child process. In order to improve efficiency, a copy-on-write strategy is adopted, that is, when creating a child process, the address space of the parent process is not copied. The parent and child processes have a common address space. Only when the child process needs to write data (such as writing data to the buffer), the address space will be copied and the buffer will be copied to the child process. Thus, the parent and child processes have independent address spaces. After executing exec after fork(), this strategy can greatly improve efficiency. If the copy is made at the beginning, then after exec, the data of the child process will be abandoned and replaced by the new process.

In the previous step, the startup parameters of the virtual machine executable program are obtained. After the startup parameters are configured, the virtual machine executable program can start working and be initialized.

The initialization can include initializing various devices. Under KVM virtualization, most devices are emulated by the QEMU software. For example, in the software module, QEMU needs to apply for various data structures to store the status of these devices and apply for various timers to simulate various clocks (RTC, ACPI PM Timer, etc.).

For example, when initializing a VCPU, under KVM virtualization, a virtual machine's VCPU runs in a QEMU thread. QEMU needs to create a thread and request various data structures to store the VCPU's state. Because the startup parameters include the specified memory address, when requesting memory for the second virtual machine, the memory address of the first virtual machine stored in the specified memory is directly used without re-requesting. Because the memory non-release flag is inherited by the parent process to the child process during fork() creation, when the child process calls exec to execute the QEMU executable program, the marked specified memory is not released and can continue to be used, thus achieving memory sharing between the first and second virtual machines.

Preferably, in an embodiment of the present application, the virtual machine executable program restores the current data of the first virtual machine in the pre-designated memory after initialization is completed. Thus, when a new virtual machine is cloned, the working capability of the original virtual machine is fully preserved.

Preferably, in an embodiment of the present application, the first virtual machine that resumes operation and the second virtual machine that starts running after fork-exec are both written to different set paths in the form of copy-on-write. Assuming that the original data storage path of the first virtual machine is vm1.qcow2, after the first virtual machine is suspended, the data written to the first virtual machine and the second virtual machine will be written to the new path. For example, the data storage path of the first virtual machine can be vm11.qcow2, and the data storage path of the second virtual machine can be vm12.qcow2. The new paths vm11.cow2 and vm12.cow2 both use vm1.qcow2 as the backing file (backup image), and use the backup image difference to generate virtual machines. A backup image is shared by multiple virtual machines, saving a lot of disk space.

Preferably, in an embodiment of the present application, before executing the second virtual machine clone, the unfinished IO of the first virtual machine backend is forcibly output to a storage medium to avoid the loss of these unfinished IO when the child process executes the exec system call. The storage medium can be the storage medium of the virtual machine, a disk on the local host, or a distributed network disk, which is not limited in the embodiment of the present application.

In this embodiment, the Linux kernel is modified so that the designated memory with a mark is not released when the exec system call is executed, thereby realizing the rapid modification and update of the startup parameters of the child process QEMU executable program; by modifying QEMU, the DONTFORK mark is not specified so that the child process generated by fork() and the parent process corresponding to the first virtual machine share the page table in a copy-on-write manner; at the same time, by calling exec() in the child process generated by fork() to execute the QEMU executable program, the rapid cloning of the virtual machine is realized, which naturally shares memory with the original virtual machine based on copy-on-write COW, and the rapid cloning of the virtual machine vmfork time is about 100ms-200ms, so that the user is not aware of it.

Figure 2 is a schematic diagram of the device structure corresponding to Example 1 of the present application. In conjunction with Figure 2, the device includes: a first preprocessing module 210, a first parameter acquisition module 220, a first cloning module 230, a first sharing module 240, a first IO output module 250, and a data recovery module 260.

The first pre-processing module 210 is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory;

The first parameter acquisition module 220 is used to obtain startup parameters of the virtual machine executable program from the designated memory;

The first cloning module 230 is configured to start the virtual machine executable program to clone the second virtual machine.

The first cloning module 230 is used to: create a child process, and the child process calls the virtual machine executable program;

The virtual machine executable program is started and initialized, and the second virtual machine is obtained after the initialization is completed.

The first cloning module 230 is configured to: enable the parent process corresponding to the first virtual machine to inherit the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

The first parameter acquisition module 210 is configured to acquire the state information of the first virtual machine from the designated memory, and update the state information of the first virtual machine to obtain the startup parameters.

The first parameter acquisition module 210 is further configured to: acquire the address of the designated memory; and pass the address of the designated memory as a new parameter into the startup parameters of the virtual machine executable program.

Furthermore, the apparatus further includes a first sharing module 240, and the first sharing module 240 is configured to: enable the child process and the parent process corresponding to the first virtual machine to share a page table in a copy-on-write manner.

Furthermore, the apparatus further includes a first IO output module 250, and the first IO output module 250 is configured to output unfinished IOs when the first virtual machine is suspended to a storage medium.

Furthermore, the apparatus further includes a first data recovery module 260, and the first data recovery module 260 is configured to obtain the data of the first virtual machine from the designated memory and recover the first virtual machine.

The device shown in FIG2 can execute the method described in the embodiment shown in FIG1 , and its implementation principle and technical effects are not described in detail any more.

FIG3 is a technical flow chart of the second embodiment of the present application. In conjunction with FIG3 , another implementation of a virtual machine cloning device under KVM virtualization in the embodiment of the present application includes:

Step S310: Pause the first virtual machine and save the data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory;

Step S320: starting the virtual machine executable program to clone the second virtual machine;

Step S330: Restore the data from the designated memory to the first virtual machine.

The execution process of the above steps is shown in the embodiment shown in FIG1 , and will not be repeated here.

It should be noted that in the embodiment of the present application, after the virtual machine executable program is initialized and the second virtual machine is cloned, the current data of the first virtual machine in the pre-designated memory can be restored. Thus, when the new virtual machine is cloned, the working capabilities of the original virtual machine are fully preserved.

FIG4 is a schematic diagram of the structure of a device according to the second embodiment of the present application. In conjunction with FIG4 , the device includes:

A second pre-processing module 410 is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory;

A second cloning module 420 is configured to start a virtual machine executable program to clone the second virtual machine;

The second data recovery module 430 is configured to recover the data from the designated memory to the first virtual machine.

The second cloning module 420 is used to: create a child process, the child process calls the virtual machine executable program; start the virtual machine executable program and initialize it, and obtain the second virtual machine after the initialization is completed.

The second cloning module 420 is configured to: cause the parent process corresponding to the first virtual machine to inherit the memory address and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory.

The data of the first virtual machine includes at least: virtual machine state information of the first virtual machine, and memory address and video memory address of the first virtual machine;

Furthermore, the apparatus further includes a second sharing module 440, and the second sharing module 440 is configured to: enable the child process and the parent process corresponding to the first virtual machine to share a page table in a copy-on-write manner.

Furthermore, the apparatus further includes a second IO output module 450, and the second IO output module 450 is configured to output the unfinished IO when the first virtual machine is suspended to a storage medium.

The device shown in FIG4 can execute the method described in the embodiment shown in FIG3 , and its implementation principle and technical effects are not described in detail any more.

Application Examples

The following section will combine Figure 3 to explain the complete process of implementing the technical solution of this application in an actual application scenario.

According to the technical solution of the present application, before cloning a virtual machine, the Linux system kernel is modified in advance so that the system does not release memory with a specified tag when calling exec.

1. Request a block of memory with a specified flag from the host, denoted as memory M. This memory is not released when the system executes an exec call. When allocating memory, the host adds a flag indicating that it will not be released during exec, and removes the default DONTFORK flag. This flagged memory is then inherited by the parent process when the child process is forked.

2. Pause the operation of the first virtual machine, where the first virtual machine is the cloned virtual machine.

3. The unfinished I/O of the first virtual machine backend is flushed to any storage medium. After the system executes the exec call, all memory except the specified reserved memory is released, including the data structure in the memory of the unfinished I/O of the backend, which will cause IO loss.

4. Save the state of the first virtual machine and the memory addresses and graphics memory addresses used by the first virtual machine to the pre-requested designated memory M. After the system executes the exec call, all memory except the reserved memory is released. Therefore, to ensure the working state of the first virtual machine after resumption, it is necessary to save the state of the first virtual machine's devices, such as the CPU, disk, and mouse.

5. Starting from the time point when the first virtual machine is paused, all data written to the first virtual machine and the second virtual machine will be stored in a COW format in another path. The path can be named after the original image name - the virtual machine.

6. Set the memory and video memory requested by QEMU for the virtual machine to be inherited by the child process. Create a child process representing the new virtual machine, i.e., the second virtual machine, through fork. Due to the characteristics of the fork function, the created child process and the parent process share memory and naturally have the COW characteristic. As shown in Figure 3, execute pid = fork() to create a child process, and pid will return two values. If the return value of pid is 0, it means that the current process is a newly created child process, and execute step 7; if the return value of pid is non-zero, it is determined that the current process is the parent process, and directly execute step 10.

7. The created child process calls exec to execute the QEMU executable program and update the startup parameters of the QEMU executable program. The specific update method is to use similar startup parameters when the parent process calls the QEMU executable program and replace the parameters as needed, such as the vnc address, virtual machine name, uuid, etc. In addition, the address of the pre-applied specified memory M must be passed as a new parameter to the startup parameters of the QEMU executable program, thereby updating the startup parameters of the QEMU executable program.

8. After the startup parameters of the QEMU executable program are updated, the QEMU executable program starts running from main and performs a series of initializations. Because the address of the specified memory M is passed in the updated startup parameters, when applying for memory for the second virtual machine, the memory address of the first virtual machine saved in M is directly used instead of applying for it again. This enables memory sharing between the old and new virtual machines, saving memory space.

9. After the QEMU executable program is initialized, the virtual machine state saved in the specified memory M is restored.

10. Release the previously requested memory M and resume the operation of the first and second virtual machines. The newly resumed first virtual machine and the newly cloned second virtual machine initially have the same operating state. This cloning process takes only 100ms-200ms from pausing the first virtual machine to resuming operation, making it virtually invisible to the user. This fast cloning process provides a good user experience.

The foregoing description shows and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the inventive concept described herein by the teachings above or by techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be within the scope of the appended claims.

Claims (26)

1. A method for cloning a virtual machine under KVM virtualization, comprising: Pausing a first virtual machine and saving data of the first virtual machine in a designated memory; wherein the data in the designated memory is not released; Obtaining startup parameters of the virtual machine executable program from the designated memory; Create a child process, which calls the virtual machine executable program; The virtual machine executable program is started and initialized, and a second virtual machine is obtained after the initialization is completed. 2. The method according to claim 1, wherein the creating a child process comprises: The parent process corresponding to the first virtual machine inherits the memory address of the first virtual machine and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory. 3. The method according to claim 1, wherein the data of the first virtual machine comprises at least: Virtual machine state information of the first virtual machine, and a memory address and a video memory address of the first virtual machine. 4. The method according to claim 3, wherein obtaining startup parameters of the virtual machine executable program from the designated memory comprises: The state information of the first virtual machine is obtained from the designated memory, and the state information of the first virtual machine is updated to obtain the startup parameters. 5. The method according to claim 4, further comprising: Obtaining the address of the specified memory; The address of the designated memory is passed as a new parameter into the startup parameters of the virtual machine executable program. 6. The method according to claim 1 or 2, further comprising: The child process and the parent process corresponding to the first virtual machine share a page table in a copy-on-write manner. 7. The method according to claim 1 or 2, further comprising: Outputting the unfinished IOs when the first virtual machine is suspended to a storage medium. 8. The method according to claim 1, further comprising: The data of the first virtual machine is obtained from the designated memory, and the first virtual machine is restored. 9. A method for cloning a virtual machine under KVM virtualization, comprising: Pausing a first virtual machine and saving data of the first virtual machine in a designated memory; wherein the data in the designated memory is not released; Create a child process, which calls the virtual machine executable program; Starting the virtual machine executable program and initializing it, and obtaining a second virtual machine after the initialization is completed; The data is restored from the designated memory to the first virtual machine. 10. The method according to claim 9, wherein the creating a child process comprises: The parent process corresponding to the first virtual machine inherits the memory address of the first virtual machine and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory. 11. The method according to claim 9, wherein the data of the first virtual machine comprises at least: Virtual machine state information of the first virtual machine, and a memory address and a video memory address of the first virtual machine. 12. The method according to claim 9 or 10, further comprising: The child process and the parent process corresponding to the first virtual machine share a page table in a copy-on-write manner. 13. The method according to claim 9 or 10, further comprising: Outputting the unfinished IOs when the first virtual machine is suspended to a storage medium. 14. A device for cloning a virtual machine under KVM virtualization, comprising: A first pre-processing module is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory; A first parameter acquisition module, configured to acquire startup parameters of the virtual machine executable program from the designated memory; The first cloning module is used to create a child process, which calls the virtual machine executable program; start the virtual machine executable program and initialize it, and obtain the second virtual machine after the initialization is completed. 15. The apparatus according to claim 14, wherein the first cloning module is configured to: The parent process corresponding to the first virtual machine inherits the memory address of the first virtual machine and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory. 16. The apparatus according to claim 14, wherein the data of the first virtual machine comprises at least: The virtual machine state information of the first virtual machine, and the memory address and video memory address of the first virtual machine. 17. The device according to claim 16, wherein the first parameter acquisition module is configured to: The state information of the first virtual machine is obtained from the designated memory, and the state information of the first virtual machine is updated to obtain the startup parameters. 18. The device according to claim 17, wherein the first parameter acquisition module is further configured to: Obtaining the address of the specified memory; The address of the designated memory is passed as a new parameter into the startup parameters of the virtual machine executable program. 19. The device according to claim 14 or 15, further comprising a first sharing module, wherein the first sharing module is configured to: The child process and the parent process corresponding to the first virtual machine share a page table in a copy-on-write manner. 20. The device according to claim 14 or 15, further comprising a first IO output module, wherein the first IO output module is configured to: Outputting the unfinished IOs when the first virtual machine is suspended to a storage medium. 21. The device according to claim 14, further comprising a first data recovery module, wherein the first data recovery module is configured to: The data of the first virtual machine is obtained from the designated memory, and the first virtual machine is restored. 22. A device for cloning a virtual machine under KVM virtualization, comprising: A second pre-processing module is configured to pause the first virtual machine and save data of the first virtual machine to a designated memory; wherein the data is not released in the designated memory; A second cloning module is configured to create a child process, which calls a virtual machine executable program; start the virtual machine executable program and initialize it, and obtain a second virtual machine after the initialization is completed; The second data recovery module is configured to recover the data from the designated memory to the first virtual machine. 23. The apparatus according to claim 22, wherein the second cloning module is configured to: The parent process corresponding to the first virtual machine inherits the memory address of the first virtual machine and the video memory address of the first virtual machine to the child process so that the second virtual machine and the first virtual machine share memory and video memory. 24. The apparatus according to claim 22, wherein the data of the first virtual machine comprises at least: Virtual machine state information of the first virtual machine, and a memory address and a video memory address of the first virtual machine. 25. The device according to claim 22 or 23, further comprising a second sharing module, wherein the second sharing module is configured to: The child process and the parent process corresponding to the first virtual machine share a page table in a copy-on-write manner. 26. The device according to claim 22 or 23, further comprising a second IO output module, wherein the second IO output module is configured to: Outputting the unfinished IOs when the first virtual machine is suspended to a storage medium.